KR20010095224A - Polyurethane Dispersions - Google Patents

Abstract

PURPOSE: Provided is a radiation curable aqueous polyurethane dispersion that exhibits both good physical surface drying before radiation curing and good grain enhancement on wood. CONSTITUTION: The radiation curable aqueous polyurethane dispersion contains 0.05 to 20 wt%(based on the weight of the non-aqueous constituents of the aqueous polyurethane dispersion) of 2,2-dimethyl-3-hydroxypropionic acid-(2,2-dimethyl-3- hydroxypropyl ester)(calculated as MW 204.3). The 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester) is chemically incorporated into the radiation curable polyurethane. The polyurethane is prepared from a hydroxyl group containing polymer having an OH number of 30 to 300 mg KOH/g and comprising a member selected from the group consisting of polyester acrylates, epoxy acrylates, polyether acrylates, urethane acrylates and unsaturated polyesters.

Description

Polyurethane Dispersions {Polyurethane Dispersions}

The present invention relates to polyurethane dispersions which cure under the action of high energy radiation and to coated substrates made from these dispersions, in particular wood and furniture.

Radiation curable polyurethane dispersions are described in EP 0 704 469, 0 753 531, 0 870 788, 0 872 502 and 0 942 022. The polyurethane dispersions described in this document exhibit good physical surface-dryability once the water has evaporated even before UV curing, and only slightly soak into absorbent substrates such as wood. Thus, these coatings only improperly emphasize the natural structure of wood, which is a phenomenon known in the art as "tissue strengthening" [Roempp Lexikon der Lacke & Druckfarben, Ulrich Zorl (ed.) Stuttgart, New York, Thieme 1998 , "wood lacquers" entry, page 289].

EP 0 012 339 describes aqueous dispersions based on radiation curable prepolymers which are stabilized by dispersion additives such as polyvinylpyrrolidone. Such dispersions show good tissue reinforcement for wood, while exhibiting no surface-dryability by water release, which is extremely undesirable in industrial coating processes. Uncured lacquer surfaces are sensitive to dust and other obstacles that may occur during handling or transport. In addition, the use of dispersing additives means that some water remains in the film after most of the water has evaporated so that the residue may cause problems with the optical properties of the film and the hardness upon curing with UV light.

Thus, prior art systems exhibit inadequate tissue strengthening when physically surface-dried, or insufficient surface drying when exhibiting good tissue strengthening.

It is an object of the present invention to provide a radiation curable polyurethane aqueous dispersion which exhibits good physical surface dryness prior to radiation curing and good tissue strengthening properties in wood.

This object can be achieved according to the present invention by incorporating a small amount of 2,2-dimethyl-3-hydroxypropionic acid- (2,2-dimethyl-3-hydroxypropyl ester) into the radiation curable polyurethane aqueous dispersion. This compound surprisingly results in significantly improved tissue reinforcement for wood when physically surface-drying a radiation curable polyurethane dispersion.

Summary of the Invention

The present invention relates to 2,2-dimethyl-3-hydroxypropionic acid- (2,2-dimethyl-3-hydroxypropyl ester) HPSNPG (calculated molecular weight 204.3) 0.05 based on the weight of the non-aqueous component of the polyurethane aqueous dispersion. It relates to a radiation-curable polyurethane aqueous dispersion containing from 20 to 20% by weight.

The invention also relates to substrates having good tissue strengthening properties, in particular coated wood substrates, coated with such polyurethane dispersions.

Preparation of polyurethane dispersions is described, for example, in Method der organischen Chemie (Houben-Weyl, supplemental and additional volumes to the 4th edition, volume E20, H. Bartl and J. Falbe (eds.), Stuttgart, New York, Thieme 1987, pp. 1659-1693. Polyurethane dispersions can be prepared by adding a di- or polyfunctional isocyanate-reactive compound (component B) to a diisocyanate or polyisocyanate (component A). The reaction may be carried out homogeneously in one or more stages, or in the case of a multistage reaction, in part of the aqueous phase, once the heavy additions have been carried out completely or partially, the dispersion step is carried out. Can be done.

Isocyanate-reactive component B) contains at least one hydrophilic compound B1. Compounds that disperse may be cationic, anionic and / or nonionic hydrophilic ether groups. Examples of compound B1 are compounds containing isocyanate-reactive groups and also sulfonium, ammonium, carboxylate or sulfonate groups, and / or polyether groups which can be converted to ionic groups by salt formation. Preferred isocyanate-reactive groups are hydroxyl and amino groups. Examples of compound B1 are bis (hydroxymethyl) propionic acid, bis (hydroxymethyl) butyric acid, hydroxypivalic acid, malic acid, glycolic acid, lactic acid, glycine, alanine, taurine and 2-aminoethylaminoethanesulfonic acid. Also suitable are polyethylene glycols, polypropylene glycols, block copolymers starting on alcohols and monomethyl ethers of such polyglycols. Bis (hydroxymethyl) propionic acid is particularly suitable.

The isocyanate-reactive component B) also contains at least one compound B2, preferably acrylate or methacrylate, containing free-radically polymerizable double bonds. Examples of such compounds include mono (meth) acrylates of dihydric alcohols such as ethanediol, isomeric propanediol and butanediol, or (meth) of polyhydric alcohols such as trimethylolpropane, glycerol and pentaerythritol containing free hydroxyl groups. Acrylates are included. Polyester acrylates containing hydroxyl groups and having an OH content of 30 to 300 mg KOH / g can also be used.

Suitable monomer components that can be used during the preparation of the hydroxy-functional polyester acrylates include the following:

1. (cyclo) alkanediols having a molecular weight of 62 to 286 [ie divalent alcohols having (alicyclic) aliphatic bonded hydroxyl groups], for example ethanediol, 1,2- and 1,3-propanediol, 1 , 2-, 1,3- and 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,2- and 1,4 Cyclohexanediol and 2-ethyl-2-butylpropanediol. Also suitable are diols containing ether groups, for example diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and polyethylene glycol, having a maximum molecular weight of about 2000, preferably about 1000, most preferred Preferably about 500 polypropylene glycol or polybutylene glycol. The reaction products of these diols with ε-caprolactone or other lactones can also be used as diols.

2. Trihydric or higher functional alcohols having a molecular weight of 92 to 254, such as glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol and sorbitol or polyethers starting from such alcohols such as trimethylolpropane 1 Reaction product of mole with 4 moles of ethylene oxide.

3. Monoalcohols such as ethanol, 1- and 2-propanol, 1- and 2-butanol, 1-hexanol, 2-ethylhexanol, cyclohexanol and benzyl alcohol.

4. Dicarboxylic acids and / or anhydrides thereof having a molecular weight of 104 to about 600, such as phthalic acid, phthalic anhydride, isophthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, cyclohexane Dicarboxylic acids, maleic anhydride, fumaric acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid and hydrogenated dimer fatty acids.

5. higher functional carboxylic acids or anhydrides thereof, such as trimellitic acid and trimellitic anhydride.

6. Monocarboxylic acids such as benzoic acid, cyclohexanecarboxylic acid, 2-ethylhexanoic acid, caproic acid, caprylic acid, capric acid, lauric acid, natural and synthetic fatty acids.

7. Acrylic acid, methacrylic acid or dimer acrylic acid.

Preferred polyester acrylates containing hydroxyl groups are the reaction products of at least one compound of group 1 or 2 and of at least one compound of group 4 or 5 and at least one compound of group 7.

Groups having a dispersing action generally known in the art as described, for example, in Progress in Organic Coatings, 9 (1981), 291-296, can be incorporated into polyester acrylates. Thus, some of the polyethylene glycol and / or methoxypolyethylene glycol may be incorporated as alcohol components. Other examples include these block copolymers starting with polyethylene glycol, polypropylene glycol and alcohols, and also monomethyl ethers of these polyglycols. Particularly suitable are polyethylene glycols of molecular weight 1500 and / or polyethylene glycol monomethyl ethers of molecular weight 500.

Particularly, some of the large amount of carboxyl groups of (meth) acrylic acid may be reacted with mono-, di- or polyepoxides. Since OH groups are produced in each epoxide / acid reaction, this reaction can be used especially when increasing the OH number of polyester acrylate. The acid value of the product obtained is less than 20 mg KOH / g, preferably less than 10 mg KOH / g, most preferably less than 5 mg KOH / g.

The preparation of polyester acrylates is described in German Patent Publication No. 4 040 290, No. 3 316 592 and in P.K.T. Oldring (ed.), Chemistry & Technology of UV & EB Formulations for Coatings, Inks & Paints, vol. 2, 1991, SITA Technology, London, pp. 123-135.

Alternatively, known epoxy acrylates containing hydroxyl groups, polyether acrylates containing hydroxyl groups or polyurethane acrylates containing hydroxyl groups and an OH content of 20 to 300 mg KOH / g, as well as their respective mixtures and Mixtures with hydroxyl group-containing unsaturated polyesters, mixtures with polyester acrylates, or mixtures of hydroxyl group-containing unsaturated polyesters and polyester acrylates can also be used. These compounds are also described in P.K.T. Oldring (ed.), Chemistry & Technology of UV & EB Formulations for Coatings, Inks & Paints, vol. 2, 1991, SITA Technology, London.

Isocyanate-reactive component B) is component B3 wherein the non-aqueous component of the polyurethane dispersion is 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester) (HPSNPG, calculated molecular weight). 204.3) 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl- in an amount containing 0.05 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. 3-hydroxypropyl ester) optionally. HPSNPG can also be incorporated as reaction products with compounds containing isocyanate groups, for example in radiation curable polyurethanes.

The isocyanate-reactive component B) may also contain, as component B4, less than 30% by weight, preferably less than 10% by weight, of diols having 2 to 10 carbon atoms. Examples include ethylene glycol, di- or triethylene glycol, 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexanediol and mixtures thereof.

The isocyanate-reactive component B) also contains, as component B5, less than 60% by weight, preferably less than 30% by weight, of high molecular weight known diols or polyols having a number average molecular weight of 400 to about 8000, preferably 500 to 4000. can do. Preference is given to polymers having about two hydroxyl functional groups. These polymers include polyester alcohols prepared from aliphatic, cycloaliphatic and / or aromatic di-, tri- and / or polycarboxylic acids and diols, triols and / or polyols, as well as lactone-based polyester alcohols; Polyetherols prepared by polymerization of cyclic ethers or reaction of alkylene oxides with starting molecules; Hydroxyl-terminated polycarbonates prepared by reaction of diols, lactone-modified diols or bisphenols (eg bisphenol A) with phosgene or carboxylic acid diesters such as diphenyl carbonate or dimethyl carbonate Nate; Hydroxyl-terminated polyamide alcohol; And hydroxyl-terminated polyacrylate diols such as Tegomer BD100 (Tego GmbH, Essen).

The isocyanate-reactive component B) also contains diamines and / or polyamines as component B6 to increase the molecular weight, preferably at the end of the polyaddition. This reaction is preferably carried out in an aqueous medium. In this case, the diamines and / or polyamines should be more reactive to the isocyanate groups of component A) than to water. Examples of suitable amines include ethylenediamine, 1,6-hexamethylenediamine, isophoronediamine, 1,3- and 1,4-phenylenediamine, 4,4'-diphenylmethanediamine, amino-functional polyethylene oxide Or polypropylene oxides (eg Jaffamine resin, D series available from Huntsman Corporation), triethylenetetramine and hydrazine. Ethylenediamine is particularly preferred.

It is also possible to add some of the monoamines such as butylamine, ethylamine and amino-functional polyethylene oxides and polypropylene oxides (eg, Jeffamine resins, M series, available from Huntsman Corporation). .

Component A) is selected from aromatic, araliphatic, aliphatic or cycloaliphatic polyisocyanates and mixtures thereof. Examples of suitable polyisocyanates include butylene diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate [2,2,4- and / or 2,4,4-trimethyl Hexamethylene diisocyanate], isomer bis (4,4'-isocyanatocyclohexyl) methane, isocyanatomethyl-1,8-octane diisocyanate, 1,4-cyclohexylene diisocyanate, 1,4-phenyl Ethylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate, 1,5-naphthylene diisocyanate, 2,4'- and / or 4,4'-diphenylmethane diisocyanate and 4,4 ', 4 "-triphenylmethane triisocyanate. Polyisocyanates containing urethane, isocyanurate, allophanate, biuret, uretidione and / or iminooxadiazinedione groups. Derivatives of are also suitable. Diisocyanate, isophorone diisocyanate, isomeric bis (4,4'-isocyanato-cyclohexyl) methane, and mixtures thereof are preferred.

The polyurethane dispersions according to the invention can be prepared using any known method, for example emulsifiers / shears, acetone, prepolymer / mixing, melting / emulsifying, ketamine and solid / simultaneous dispersion methods or derivatives thereof. have. This method is described in Methode der organischen Chemie (Houben-Weyl, supplemental and additional volumes to the 4th edition, volume E20, H. Bartl and J. Falbe (eds.), Stuttgart, New York, Thieme 1987, pp. 1671- 1682. Melt / emulsification and acetone methods are preferred, acetone methods are particularly preferred.

If required by the method (eg acetone method, optionally melting / emulsifying method), component A) and B) without B6 are initially introduced into the reactor to produce an intermediate product (prepolymer). They are diluted (preferably in a solvent-free melting / emulsification process) with a solvent which is water immiscible or inert to isocyanate groups and heated at relatively high temperatures, in particular between 50 and 120 ° C. Suitable solvents include acetone, butanone, tetrahydrofuran, dioxane, acetonitrile, dipropylene glycol dimethyl ether and 1-methyl-2-pyrrolidone. Catalysts known to accelerate isocyanate addition reactions (eg triethylamine, 1,4-diazabicyclo [2.2.2] octane, tin dioctoate or dibutyltin dilaurate) are also added to the initial mixture. Can be introduced.

Polyisocyanate or polyisocyanates A) are added dropwise to these mixtures. The molar ratio of isocyanate groups in component A) to isocyanate-reactive groups in component B) is from 1: 1 to 1: 5, preferably from 1: 1.1 to 1: 1.5. The reaction of components A) and B) is carried out up to 65-100%, preferably 80-100% conversion, based on the NCO groups in (A). In any embodiment of this method, the reaction may continue until the NCO content of the reaction mixture remains constant.

The degree of conversion was conventionally determined by monitoring the NCO content of the reaction mixture. This can be achieved by both microscopic measurements (IR or NIR spectra) and chemical analysis (titration) of samples taken from the mixture. Once the desired NCO content is reached, the temperature is reduced as soon as possible to significantly reduce any further reaction rate of components A) and B). The extent to which the reaction temperature is reduced is determined by the reactants used (in particular, the reactivity of the different isocyanates may vary significantly) and can be confirmed by continuing to monitor the NCO content of the mixture.

Once the prepolymer is produced, salt formation of possible anionic and cationic groups of component B1 is carried out if salt formation on the starting molecule has not yet been carried out. In the case of anionic groups it is advantageous to use a base (for example ammonia, triethylamine, triethanolamine, potassium hydroxide or sodium carbonate) and in the case of cationic groups it will be advantageous to use dimethyl sulfate or succinic acid. If only compound B1 contains an ether group, the neutralization step is omitted.

In the final reaction step of one embodiment, when the molecular weight increase and formation of the polyurethane dispersion of the present invention takes place in an aqueous medium, it contains polyamines or polyamines B6 while applying a strong shearing force such as optionally stirring the prepolymer Or the dispersion / polyamine D mixture is stirred with the prepolymer. The dispersion according to the invention is then formed by the reaction of isocyanate groups still present in the prepolymer with amino groups from component B6 to increase the molecular weight.

The amount of polyamine B6 depends on the unreacted isocyanate groups still present. It is not necessary to react all isocyanate groups still present with the polyamine B6. The unreacted isocyanate group then reacts slowly with water. Preferably more than 50%, more preferably more than 75% of isocyanate groups are reacted with polyamine B6.

In one embodiment of the process, the amino groups are added in an amount sufficient to react with 180%, preferably 101-120%, above 100% of the previously unreacted isocyanate groups. In this case, some amino groups remain unreacted.

In a further variant of the process, the dispersing step can first be carried out, advantageously adding component (B6) diluted with water.

If desired, any organic solvent present can be removed by distillation. The dispersion obtained has a solids content of 20 to 60% by weight, preferably 30 to 55% by weight.

Once the water has evaporated, the polyester acrylate urethane dispersions according to the invention become a rigid, mechanically loadable coating upon drying without the addition of additives. Subsequently, while inducing crosslinking using radiation-chemicals and / or glass-radical means, the film is cured completely to provide a coating having particularly high quality of chemical and chemical resistance.

Particular preference is given to UV curing among radiation-chemically induced polymerizations (UV, electron, X-ray or gamma radiation). UV curing is carried out in the presence of a photoinitiator. Suitable photoinitiators include aromatic ketone compounds such as benzophenone, alkylbenzophenones, 4,4'-bis (dimethylamino) -benzophenones (Michler ketones), anthrones and halogenated benzophenones. Also suitable are acyl phosphine oxides, such as 2,4,6-trimethylbenzoyldiphenyl phosphine oxide, phenyl glyoxylic acid esters, anthraquinones and derivatives thereof, benzyl ketals and hydroxyalkylphenones. Mixtures of these compounds can also be used.

When cured by free-radical means, aqueous emulsions of water soluble peroxides or water insoluble initiators are suitable. Such free radical formers can be combined with promoters in a known manner.

The polyurethane dispersions according to the invention can be applied to suitable substrates by known methods such as spraying, roll coating, knife coating, flooding, brushing or dipping. Applying the polyurethane dispersion according to the invention to wood, particularly good surface optical properties and natural pattern of wood are emphasized (tissue strengthening), resulting in an excellent surface. The polyurethane dispersions according to the invention are therefore particularly suitable for multilayer coatings of primers, for example pre-finished parquet floors. The primer can then be overcoated with other coating compositions known for parquet floor coatings, for example UV cured polyurethane aqueous dispersions or 100% UV cured polyester acrylates and / or urethane acrylates.

Other absorbent substrates (eg paper, paperboard or leather), metals, plastics and precoated substrates can also be coated with the polyurethane dispersions according to the invention.

The polyurethane dispersions according to the invention can be used as sole lacquer binders or in combination with other binders and additives known in the lacquer art, for example dispersions, pigments, dyes or flatting agents. In particular, combinations with other polyurethane dispersions or polyacrylate dispersions are preferred.

<Example>

Example 1 Dispersion A (Comparative Example According to European Patent Publication No. 0 753 531 and US Patent No. 5,684,081)

342.9 g of polyester acrylate (Laromer PE 44F, available from BASF AG, Ludwigshafen, Germany), 57.1 g of polyester acrylate (IRR 322, commercially available from UCB SA of Drogenbosch, Belgium) 10.4 g of neopentyl glycol, 26.80 g of dimethylolpropionic acid, 0.6 g of dibutyltin dilaurate and 194.0 g of acetone were first introduced into a reactor equipped with a stirrer, an internal thermometer and a gas inlet (air streams 2-3 l / h). . Next, 102.1 g of isophorone diisocyanate (Desmodur I available from Bayer AG, Leverkusen, Germany) and hexamethylene diisocyanate (Desmodur H marketed from Bayer AG, Leverkusen, Germany) 50.4 g) were added and heated to obtain a constant acetone reflux. The mixture was stirred at this temperature so that the NCO content of the reaction mixture was 2.0 ± 0.1% by weight.

Then the temperature was reduced to 40 ° C. and 20.2 g of triethylamine were added quickly. After 10 minutes the reaction mixture was poured into 1170.0 g of water at 20 ° C. with rapid stirring. Once the dispersion was formed, 10.2 g of ethylenediamine in 30.0 g of water were added.

After stirring for 30 minutes without heating or cooling, the product was evaporated under reduced pressure (50 mbar, up to 50 ° C.) until a solid content of 37 ± 2 wt% was obtained.

Example 2: Dispersion B According to the Present Invention

342.9 g of polyester acrylate (Laromer PE 44F, available from BASF AG, Ludwigshafen, Germany), 57.1 g of polyester acrylate (IRR 322, commercially available from UCB SA, Droggenbos, Belgium), neopentyl glycol 9.4 g, 2,2-dimethyl-3-hydroxypropionic acid- (2,2-dimethyl-3-hydroxypropyl ester) (commercially available from BASF AG, Ludwigshafen, Germany) 1.8 g, dimethylolpropionic acid 26.80 g , 0.6 g of dibutyltin dilaurate and 194.0 g of acetone were first introduced into a reactor equipped with a stirrer, an internal thermometer and a gas inlet (air stream 2-3 L / h). Next, 102.1 g of isophorone diisocyanate (Desmodur I, commercially available from Bayer AG, Leverkusen, Germany) and 50.4 g of hexamethylene diisocyanate (Desmodour H, commercially available from Bayer AG, Leverkusen, Germany) Was added and heated to obtain a constant acetone reflux. The mixture was stirred at this temperature so that the NCO content of the reaction mixture was 2.0 ± 0.1% by weight.

Then the temperature was reduced to 40 ° C. and 20.2 g of triethylamine were added quickly. After 10 minutes the reaction mixture was poured into 1170.0 g of water at 20 ° C. with rapid stirring. Once the dispersion was formed, 10.2 g of ethylenediamine in 30.0 g of water were added.

After stirring for 30 minutes without heating or cooling, the product was evaporated under reduced pressure (50 mbar, up to 50 ° C.) until a solid content of 37 ± 2 wt% was obtained.

Example 3: Dispersion C According to the Present Invention

400.0 g of polyester acrylate (Laromer PE 44F, available from BASF AG, Ludwigshafen, Germany) having an OH value of about 80 mg KOH / g was 10.4 g of neopentyl glycol, 2,2-dimethyl-3-hydroxypropionic acid. 1.0 g of (2,2-dimethyl-3-hydroxypropyl ester) (available from BASF AG, Ludwigshafen, Germany), 26.80 g of dimethylolpropionic acid, 0.6 g of dibutyltin dilaurate and 186.3 g of acetone. It was first introduced into a reactor equipped with a stirrer, an internal thermometer and a gas inlet (air stream 2-3 L / h). Next, 101.8 g of isophorone diisocyanate (Desmodur I commercially available from Bayer AG, Leverkusen, Germany) and 51.1 g of hexamethylene diisocyanate (Desmodur H commercially available from Bayer AG, Leverkusen, Germany) Was added and heated to obtain a constant acetone reflux. The mixture was stirred at this temperature so that the NCO content of the reaction mixture was 2.0 ± 0.1% by weight.

Then the temperature was reduced to 40 ° C. and 20.2 g of triethylamine were added quickly. After 10 minutes the reaction mixture was poured into 1030.0 g of water at 20 ° C. with rapid stirring. Once the dispersion had formed, 9.9 g of ethylenediamine in 30.0 g of water were added.

After stirring for 30 minutes without heating or cooling, the product was evaporated under reduced pressure (50 mbar, up to 50 ° C.) until a solid content of 38 ± 2 wt% was obtained.

Real example:

A (comparative) B C Solid content One) 38.7% by weight 36.5 wt% 37.5 wt% pH 2) 8.6 8.7 8.6 Viscosity 3) 25 mPa 30 mPa 26 mPa Appearance of dispersion 4) Slightly colloidal Slightly colloidal Slightly colloidal Physical surface-dry 5) 12 18 15 Pendulum strength 6) a) 153b) 143c) 124 a) 161b) 146c) 135 a) 165b) 165c) 140 Granularity 7) 91 94 54 Organizational Strengthening 8) 5 3 2 Water resistance 9) 0 0 0 Ethanol Resistance 10) 0 0 0 1) DIN EN ISO 3251 (1 g, 125 ° C) 2) DIN 537853) Rotary viscometer, 23 ° C 4) Visual evaluation 5) Binder dispersion + 1.5% Irgacure 500 additive [Lampertime, Germany Commercially available from Ciba Specialties; Wet film 150 μm; 60 minutes drying at 20-23 ° C .; Koenig pendulum hardness measurement. 6) Binder dispersion + 1.5% Irgacure 500 additive (commercially available from Ciba Specialty, Lampertime, Germany); Wet film 150 μm; 60 minutes drying at 20-23 ° C .; UV curing, Hg lamp 80 W / cm, a) flow rate 3 m / min; b) flow rate 5 m / min; c) flow rate 10 m / min; Jannik Pendulum Hardness Measurement. 7) Average particle size by laser correlation spectroscopy: Zeta-Sizer 1000.8) Walnut wood film commercially available from Malvern Instruments, Melbourne, UK, 6); Visual evaluation by rating: rating 0 = best result; Grade 5 = worst result. To make a better comparison, several commercially available radiation curable aqueous binders were simultaneously tested and evaluated: 1. Laromer PE 55W polyester acrylate (commercially available from BASF AG, Ludwigshafen, Germany) in a physically surface-free protective colloidal emulsion: tissue strengthening grade 0; IRR 400 PU dispersion (commercially available from UCB SA, Drogogenbos, Belgium), Physically Surface-Drying: Tissue Strengthening Grade 4; Ucecoat DW 7770 PU dispersion (commercially available from UCB SA, Drogogenbos, Belgium), Physically Surface-Drying: Tissue Strengthening Grade 5: 4. NeoRad R450 PU dispersion (commercially available from Zeneca Resins, Walwick, The Netherlands), physically surface-drying: tissue strengthening grade 5.9) Cross-coating application using a box knife applicator; 6) apply 2 ^* 150 μm wet film to maple while medium drying and sanding between coatings; Exposure for 16 hours (see DIN 68861) (2 ^* = 2 films). 10) See 9).

Comparing dispersions A and B, incorporating a small amount of 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester) into dispersion B still provides good physical surface-drying properties. It has been demonstrated that the reinforcement of tissue in wood is clearly improved.

While the invention has been described in detail above for purposes of illustration, such details are for illustrative purposes only and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention, except as may be defined by the claims. I will understand that you can lose.

Incorporation of a small amount of 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester) into the dispersion according to the invention results in good physical surface dryness prior to radiation curing and good tissue strengthening in wood A radiation curable polyurethane aqueous dispersion is provided that exhibits properties.

Claims (8)

0.05 to 20 wt% 2,2-dimethyl-3-hydroxypropionic acid- (2,2-dimethyl-3-hydroxypropyl ester) (calculated molecular weight 204.3) based on the weight of the non-aqueous component of the polyurethane aqueous dispersion Radiation curable polyurethane aqueous dispersion containing a. The radiation curable polyurethane aqueous dispersion according to claim 1, wherein 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester) is chemically incorporated into the radiation curable polyurethane. The method of claim 1 wherein the polyurethane has an OH number of 30 to 300 mg KOH / g and comprises a member selected from the group consisting of polyester acrylates, epoxy acrylates, polyether acrylates, urethane acrylates and unsaturated polyesters. A radiation curable polyurethane aqueous dispersion prepared from a hydroxyl group containing polymer. The polyurethane of claim 2 wherein the polyurethane has an OH number of 30 to 300 mg KOH / g and comprises a member selected from the group consisting of polyester acrylates, epoxy acrylates, polyether acrylates, urethane acrylates and unsaturated polyesters. A radiation curable polyurethane aqueous dispersion prepared from a hydroxyl group containing polymer. The radiation curable polyurethane number according to claim 1, wherein the polyurethane is made from a hydroxyl group containing polymer having an OH number of 40 to 200 mg KOH / g and comprising a member selected from the group consisting of polyester acrylates and epoxy acrylates. Dispersion. 3. The radiation curable polyurethane number according to claim 2, wherein the polyurethane is made from a hydroxyl group containing polymer having an OH number of 40 to 200 mg KOH / g and comprising a member selected from the group consisting of polyester acrylates and epoxy acrylates. Dispersion. A substrate coated with the radiation curable polyurethane aqueous dispersion of claim 1. A wood substrate coated with the radiation curable polyurethane aqueous dispersion of claim 1, wherein the coating provides good tissue strengthening properties to the wood substrate.